1. Field of the Invention
The present invention relates to a paste composition and a printed circuit board using the same.
2. Description of the Background Art
Batteries that are small in size and have high capacity are desired for mobile equipment such as cellular telephones. Therefore, fuel cells capable of providing higher energy density than conventional batteries such as lithium secondary batteries have been developed. Examples of the fuel cells include a direct methanol fuel cell.
In the direct methanol fuel cell, methanol is decomposed by a catalyst, forming hydrogen ions. The hydrogen ions are reacted with oxygen in the air to generate electrical power. In this case, chemical energy can be converted into electrical energy with extremely high efficiency, so that significantly high energy density can be obtained.
A flexible printed circuit board (hereinafter abbreviated as an FPC board), for example, is provided as a collector circuit within such a direct methanol fuel cell (see JP 2004-200064 A, for example).
The FPC board has a configuration in which a conductor layer is formed on a base insulating layer having flexibility. A part of the FPC board is drawn out of the fuel cell. Various external circuits are connected to the part of the FPC board that is drawn out of the fuel cell.
When methanol supplied as a fuel to the direct methanol fuel cell reacts with oxygen, formic acid having a strong corrosive effect is formed. The formic acid causes the conductor layer of the FPC board to corrode.